The idea for this came from an interesting piece of psychology I learned of years ago that I’ve since applied to my research and design repertoire in logo design. It’s a very simple maxim and runs like this:

People recognise objects by shape first then colour.

Or, as noted in Hilgard’s Introduction to Psychology by Aktinson et al.:

To recognise an object it is primarily shape, alongside size, colour, texture and orientation which we use to do so.